The presently described embodiments relate to a portable marking device for use with transient document media. It finds particular application in annotating such transient document media, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiments are also amenable to other like applications.
By way of background, many paper documents are-discarded after being read. Although paper is inexpensive, the quantity of discarded paper documents is enormous and the disposal of these discarded paper products raises significant cost and environmental issues.
To address this problem, transient document media systems have been developed. Transient document media is a media designed to replace conventional paper for some applications. It is typically marked upon using ultraviolet (UV) light and typically erased with heat. It is designed so that the media, or paper, may be reused with different images rendered thereon so one can replace paper printing in some applications.
In this regard, transient document media involves providing a reimagable medium comprised of a substrate and a photochromic material, wherein the medium is capable of exhibiting a color contrast and an absence of the color contrast. The reimagable medium is exposed to an imaging light corresponding to a predetermined image to result in an exposed region and a non-exposed region. The color contrast is present between the exposed region and the non-exposed region to allow a temporary image corresponding to the predetermined image to be visible to the naked eye.
In one form, this type of marking on paper can be accomplished by using paper having a particular dye coated thereon. Exposed regions of the dyed paper may then be excited by a radiation source such as ultraviolet light.
To erase the temporary image, transient document media systems subject a temporary image to an indoor ambient condition for a time period. This serves to change the color contrast to erase the temporary image without using an image erasure device. Thus, the temporary image is visible for a time sufficient for the observer to view the temporary image. However, the visible time is limited to permit the optional feature of repeating the procedure as described. So, the temporary image information and temporary image erasure may be performed a number of times on the same media. In some forms, the reimagable medium may be considered self-erasing.
Transient document systems of this type are described in U.S. Publication No. US 2005/0244742 A1, entitled “Reimagable Medium with Light Absorbing Material,” filed Apr. 29, 2004, U.S. Publication No. US 2005/0244743 A1, entitled “Reimagable Medium,” filed Apr. 29, 2004, and U.S. Publication No. US 2005/0244744 A1, entitled “Method for Forming Temporary Image,” filed Apr. 29, 2004, all of which are incorporated herein by this reference.
In some applications, users may wish to annotate media having temporary images formed thereon. However, if traditional marking pens are used on the media, a difficulty may arise. That is, because the transient document media is reusable, any annotations written by the user on the media using a conventional marking pen will be seen by the next user. As such, transient document media systems could be improved.
A variety of light and/or marking pens are known. At least some of these known pens have been used for preventing fraud and the like, or for writing in invisible ink. For example, U.S. Pat. No. 6,860,616 discloses a pen that writes with fluorescent ink. An ultraviolet light emitting diode (LED) is provided to the pen to illuminate the ink as it is written. It should be noted that this pen, however, does not excite the ink prior to writing and may well be limited to fluorescent inks.